Researchers in New York have induced mice to run and lose control of their extremities on demand by activating small groups of cells in their brains via magnetism.
So-called magneto-thermal stimulation allows for a remote, minimally invasive way to trigger activity deep in the brain by turning cells on and off.
Said lead researcher Arnd Pralle from the University at Buffalo: “There is a lot of work being done now to map the neuronal circuits that control behavior and emotions…. How is the computer of our mind working? The technique we have developed could aid this effort greatly.” The study was published in the peer-reviewed journal eLife.
Magneto-thermal stimulation uses magnetic nanoparticles to stimulate neurons outfitted with temperature-sensitive ion channels. First, scientists introduce a special strand of DNA into targeted neurons that causes them to produce a heat-activated ion channel. They then inject magnetic nanoparticles into the same area of the brain, which attach to the surface of the targeted neurons. When an alternating magnetic field is applied to the brain, it causes the nanoparticles’ magnetization to flip rapidly, generating heat that warms the targeted cells, causing the channels to open and activating the cells. Doing so, the researchers were able to activate three regions in the mice brains, causing specific movements. One region caused the mice to run, another to turn around, and another to become unable to move their extremities.
Said Pralle: “Using our method, we can target a very small group of cells, an area about 100 micrometers across, which is about the width of a human hair.” Pralle had previously activated neurons in a petri dish, and then in C. elegans, a tiny nematode. Unlike some other methods of stimulating brain cells — like optogenetics — magneto-thermal stimulation requires no equipment implants. Pralle said that even after the brains of mice were repeatedly stimulated the targeted neurons showed no signs of damage.